When joints of pipe are subjected to a combination of tension loads and oscillatory bending loads, such loadings can cause stress reversals which, in turn, can cause the connection to fail. Such loadings are a particular issue when pipe joints are connected as part of a riser pipe extending vertically between a wellhead, x-mas tree, and an offshore location and a tensioning device or supporting device aboard a drilling vessel from which operations could be conducted. The riser pipe, which can extend to a length of several thousand feet, is not only subjected to tension loads as the vessel rises and falls on the water level, but also to bending loads due to the water currents. To deal with such situations, a pipe connector has been proposed in U.S. Pat. No. 4,012,059 where a part of the joint is stretched to preload it while the preload is held by rotation of a nut to make-up any slack caused by the tensioning of a portion of the joint. Some of the disadvantages of this technique are that each joint has to be specially designed and that the nut has to be rotated with appropriate power tools for each joint to hold the desired tension. Thus, a large nut must be operated with a wrench while the two components of the joint are pushed together and the pin is under a tensile stress. The nut is mounted to the box and is rotated with a wrench until it engages the pin. The joint construction is complicated, making each joint expensive to manufacture such that the entire riser string which contains numerous joints winds up being a substantial investment for the well operator. Additionally, there are hazards involved in operation of the nut while one component of the joint is subjected to stresses. Finally, the amount of residual strain in the joint is variable because it is a function of the final position of the nut which is turned while the pin is under a stress loading.
Other patents that illustrate generally different kinds of joints used in subsea risers are seen in the following U.S. Pat. Nos.: 3,189,372; 3,508,609; 4,185,856; 4,062,571; 5,404,832; 4,844,511; 4,436,325; 4,696,494; 4,902,046; 5,141,257; 5,098,132; and 3,948,545, which illustrates a breech lock type of a connection.
What has been missing in the prior art described above is a joint of simple construction that can lend itself to rapid deployment while at the same time being of a low-cost design. The joint can be assembled quickly to provide a positive preload riser connection which has a robust design with enhanced fatigue-resistant operation in a wide variety of water depths, environmental conditions, and riser lengths. One of the objectives of the invention is to provide a riser connector and deployment system which can be used with drilling, workover, completion, intervention, or production operations for conventional vessel riser supporting techniques or self-supporting freestanding buoyant riser applications. Another objective of the invention is to provide equipment which will facilitate the rapid make-up and/or release of each joint. Yet another objective is to provide a high-strength joint that will provide the performance capability of oilfield premium joints. Another objective is to be able to provide a joint which can be made-up quickly and disassembled quickly and safely. Simplicity of the design and strength and performance are also objectives of the joint in question. Those and other objectives will be evident from a review of the preferred embodiment of the invention described below.